Striping of vinyl resin coated wires with ketone dye solutions



R. J. BROWN STRIPING OF VINYL RESIN COATED WIRES June 21, 1949.

WITH xmoun 1m: sommous Filed Nov. 15, 1944 ATTORNEYS Patented June 21, 1949 STRIPING OF VINYL RESIN COATED WIRES WITH KETONE DYE SOLUTIONS Richard J. Brown, Hastings on Hudson, N. Y., as-

signor to Anaconda Wire and Cable Company, a corporation of Delaware Application November 15, 1944, Serial No. 563,542

2 Claims.

This invention relates to electrical conductors insulated with a plastic coating or sheath and has for its object an improved method of producing such electrical insulated conductors. More particularly, the invention provides a method of impregnating the exterior surface with dyes in solution to give the coating or sheath of plastic material a permanent identifying color. The invention is especially concerned with plastic sheaths formed of synthetic resins and pro vides a method of impregnating the exterior surface of the sheath with a color imparting organic liquid which is preferably a solvent for the plastic material and which carries the color into the body of the plastic. Advantageously the color may be applied by using a solvent for the resinous plastic material containing in solution an organic dye. One or several different colors may be applied to the exterior surface. It is an important feature of the invention that the surface of the sheath, except for its imparted color, remains substantially unchanged.

It has been the common practice heretofore to apply to the exterior surface of plastic sheaths a coating of identifying paint. Paint has considerable body and actually increases the diameter of the conductor. Moreover, paints are usually quite brittle and tend to flake off, resulting in an inferior surface condition. It has also been common practice to form sheaths of insulation formed of pigmented or otherwise colcred synthetic materials but this has required the conversion of the entire mass of plastic to a colored state in advance of forming the sheath,

necessitating the use of an excessive amount of z.

coloring material frequently with an objectionable efiect upon the flow and setting properties of the resins. Perhaps the most significant drawback to the use of such colored plastics is that but a single color may be used.

I have discovered that resinous plastic coatings or sheaths on electrical conductors may be surface impregnated with small quantities of organic dyes preferably dissolved in easily volatilizable solvents which are penetrants, and especially solvents or swelling agents for the plastics. I have found that certain dye solutions do not change the properties of the resin, do not increase the diameter of the sheath, and that the dye is not impaired in the handling of the conductors, or by moisture or by petroleum oils and the like. One important and significant feature of the invention is that several different dyes may be applied to the same sheath, for example as stripes, longitudinal or helical, or at suitably spaced intervals. Water-insoluble dyes in organic solvents may be used with the result that multi-colored insulation may be produced, the colors of which are permanent and do not merge or diffuse when wet. The invention, accordingly, provides a method of applying one or more identifying colors to the exterior of a resinous plastic insulating sheath or coating in an easily volatilizable organic solvent which deposits the dye in the exterior of the sheath.

In practicing a method of the invention, various synthetic resinous materials may be used including methyl methacrylate, nylon, ethylcellulose, cellulose acetate, cellulose acetate (high acetyl), cellulose acetatebutyrate, cellulose nitrate (pyroxylin). The most effective synthetic resins which I have found for practicing the invention are polyvinyl chloride and copolymerized vinyl chloride-vinyl-acetate resins. It is important to select a dye that dissolves in a solvent for the plastic material. The foregoing plastics are generally soluble in ketones, and acetone or methyl ethyl ketone are especially effective solvents for use in the invention. I have found that dyes of the anthroquinone and celanthrene groups are especially suitable since they are soluble ketones and leave a very stable permanent color in the exterior of the plastic sheath.

The accompanying drawings illustrate, more or less diagrammatically, arrangements of apparatus which may be used in carrying out the invention, in which:

Fig. 1 is a side elevational view of one arrangement of apparatus;

Fig. 2 is a side elevation of another arrangement of apparatus, and

Fig. 3 is a fragmentary enlargement of a detail of the apparatus of Fig. 2.

In carrying out a method of the invention with a wire covered with a coating or sheath, for example, of a polyvinyl chloride or copolymerized vinyl chloride-vinylacetate resin, I may use a ketone as a solvent for the resin and for the dye, for example, acetone or methyl ethyl ketone and dissolve therein a small quantity of a suitable dye, for example anthroquinone blue. Other colors and solvents may, of course, be used for these resins. The amount of dye is relatively small and may vary, for example, from 0.5% to 2.5% by weight based upon the particular color used. The aforementioned dyes are especially effective because they are resistant to aromatic chemicals, to gasoline and petroleum oils and do not dissolve in, or otherwise wash off, the sheath. This is important because a sheath covered with several different identifying colors must have permanent colors that no not merge or become diffused in each other with the resulting loss of the identifying-markings.

It is not only important to use a solvent for the dye but a solvent which also dissolves and, accordingly, penetrates the exterior surface of the resin. The solvent action on the resin may result in a softening or swelling and it is, accordingly, one of the objects of the invention to use a solvent which is highly volatile and which may easily be disposed of by evaporation, thereby restoring the exterior of the resinous sheath to its permanent condition. This enables the insulated conductor to be dyed and be disposed of expeditiously, for example, as by winding on reels for storage and shipment.

Fig. 1 illustrates an arrangement of apparatus in which the sheathed wire from the reel l passes. over direction pulley 2 and then over pulley 3 submerged in the dye solution 6 in a suitable vessel 5. During the passage of the insulated conductor through the solution, there is a sufiicient absorption of the dye solution into the body of the resinous plastic sheath to impart thereto a permanent color. Ordinarily this penetration may be around 0.01 inch in thickness, more or less, and, consequently, a volatile solvent, such as acetone, will dry within from 3 to seconds. The

wire passes in an upright direction over pulleys 1 and 8 to the reel 9. In an arrangement of apparatus such as that illustrated, the wire may be passed through the apparatus at the rate of around 50' feet per minute. The solvent may, accordingly, be evaporated and the wire dried before it reaches the reel 9.

In order to effect a relatively deep penetration of the dye solution, I may wrap the conductor one or more times around the pulley 3 which i submerged in the solution or use a relatively long dye trough toincrease the time during which the conductor is in contact with the solution. The evaporation of the solvent and the consequent drying of the sheath may be speeded up by first wiping off the excess solvent and then passing the conductor through an electric oven to forcedry the conductor.

The apparatus of Fig, 1 is especially useful in applying a single color, for example red or blue, to the entire surface of the sheath. The apparatus of Fig. 2, however, may be used to apply one or more longitudinal or helical stripes to the sheath. These stripes may be applied to the original uncolored sheath or to a sheath previously dyed, as in the apparatus of Fig. 1. The sheathed wire from the reel l passes over direction pulley 2, upwardly to pulley I and thence over pulley 8 to the reel 9. The dye solution is placed in the dye pots I0 and l l which have lateral tubes l2 and 13 with pen points [4 and I5, respectively. The sheathed wire passes in contact with the pen points and a carefully regulated, and preferably narrow, strip of the solution is applied to the sheath to form the colored stripes. I may use, for example, a red solution in pot Ill and a blue solution in pot I l, applying these, for example, to a white or yellow exteriorly colored sheath and thereby obtaining a conductor with three different colors. The stripes are longitudinally applied when the pen points are in a stationary position.

I may, however, apply the helical stripes l5, as illustrated in Fig. 3, and, to this end, the supporting platform I] on which the dye pots are mounted may be rotated by means well known in the art during the longitudinal movement of the wire.

I claim:

1. The method of applying at least one identifying colored stripe to the exterior of a sheath of resinous material from the class consisting of polyvinyl chloride and copolymerized vinyl chloride-vinylacetate resins surrounding a wire, which comprises applying to the exterior of the sheath a stripe consisting of a highly volatile liquid ketone in which the resinous sheath is soluble and which contains in solution an organic dye, maintaining the sheath in contact with the so lution for only a suflicient period of time to effect the penetration of the solution and dye into a thin surface layer at the exterior of the sheath along the stripe, and evaporating the ketone from the solution substantially completely Within three to five seconds after the solution has been applied to the sheath, thereby forming a sharply defined colored stripe at the surface of the sheath while leaving the remainder of the sheath unaffected by the dye.

2. The method of applying one or more identifying colored helical stripes to the exterior of a wire sheath with a resinous material from the class consisting of polyvinyl chloride and copolymerized vinyl chloride vinyl acetate resins, which comprises drawing the sheathed wire longitudinally over a pen that is kept supplied with a solution consisting of a highly volatile liquid ketone in which the resinous plastic material of the sheath is soluble and which contains in solution an organic dye, thereby forming a stripe of the dye-containing solution on the wire sheath, rotating the pen about thewire as the wire is drawn thereover, whereby the sheath is formed helically about the wire, and evaporating the ketone from the solution within three to five seconds after the application of the solution, thereby leaving the dye impregnated only in a thin surface skin at the exterior of the sheath and forming a sharply defined colored helical stripe with the main body of the sheath being unaifected by the dye.

RICHARD J. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,126,810 Pugh Aug. 16, 1933 2,188,160 Rooney et al Jan. 23, 1940 2,260,543 Smith Oct. 28, 1941 2,273,305 Whitehead Feb. 1'7, 1942 2,274,751 Sowter Mar. 3, 1942 2,347,508 Rugely Apr. 25, 1944 2,380,503 Croft July 31, 1945 2,428,284 Krogel Sept. 30, 1947 OTHER REFERENCES American Dyestufi Reporter for October 27, 1941, page 575; article in Vinyon Synthetic Fibers, by Karl Heymann. 

